Solar Thermal Panels Covered by Solar PV Panels?

[sandiegolloyd]

Hi , I am designing a solar PV system for my south facing roof. Unfortunately I already have my Solar Therm. panels already located there for my pool. Can I just install them over the same location about six inches above the therm. panels? Or would that reduce the efficiency of the thermal panel by too much? I was hoping that the heat developed by the solar PV panel would transfer to the solar thermal panel and thus the thermal panel function would not be reduced too much. Anyone know for sure?
thanks!

[Ward L]

Radiant Heat Transfer

Hi , I am designing a solar PV system for my south facing roof. Unfortunately I already have my Solar Therm. panels already located there for my pool. Can I just install them over the same location about six inches above the therm. panels? Or would that reduce the efficiency of the thermal panel by too much? I was hoping that the heat developed by the solar PV panel would transfer to the solar thermal panel and thus the thermal panel function would not be reduced too much. Anyone know for sure?
thanks!

The most efficient means of heat transfer is radiant. Sun energy is radiant. You cover your thermal system with your PV system and your thermal system will not generate much heat if any.

[russ]

You would get almost nothing from the solar thermal panels.

[inetdog]

The six inch spacing will allow too much cooling by air circulation, even if the waste heat from the back of the PV panels was large enough to be useful.

That part of the solar energy that is not reflected (hopefully less than 4%) or converted to electricity (less than 20%) will be rejected by the PV panels through radiation and conduction out the front just as heavily as out the back.
So even in the best of all possible worlds, you would get less than 40% of what you are getting without the PV panels there.
Throw in the air gap and you will be lucky to get 5% of the solar heating you have now.

To get the thermal panels to work, you would need to somehow insulate the PV panels to keep their temperature high. But that high temperature will decrease the output and life of the PV panels.
For now, the two goals are incompatible.

For what it is worth, since pool panels operate at a lower temperature than domestic hot water panels, you at least have that going in your favor.
But the end result is still going to be unsatisfactory.

[J.P.M.]

Hi , I am designing a solar PV system for my south facing roof. Unfortunately I already have my Solar Therm. panels already located there for my pool. Can I just install them over the same location about six inches above the therm. panels? Or would that reduce the efficiency of the thermal panel by too much? I was hoping that the heat developed by the solar PV panel would transfer to the solar thermal panel and thus the thermal panel function would not be reduced too much. Anyone know for sure?
thanks!

If you do this, the solar thermal panels will not produce enough useful output to measure much less use.